Polyphenol-Rich <i>Larix decidua</i> Bark Extract with Antimicrobial Activity against Respiratory-Tract Pathogens: A Novel Bioactive Ingredient with Potential Pharmaceutical and Nutraceutical Applications

• Main Authors: Marta Faggian (Author), Giulia Bernabè (Author), Sara Ferrari (Author), Stefano Francescato (Author), Gianni Baratto (Author), Ignazio Castagliuolo (Author), Stefano Dall'Acqua (Author), Gregorio Peron (Author)
• Format: Book
• Published: MDPI AG, 2021-06-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

Larch (<i>Larix decidua</i>) bark is a sawmill waste, traditionally used for antiseptic, expectorant and dermatological (wound healing, eczema, psoriasis) purposes. In this work, we developed a food-grade dry larch bark extract (LBE) from sawmill by-products using hydro-alcoholic extraction. The antibacterial activity of LBE was evaluated against respiratory-tract pathogens, i.e., <i>Staphylococcus aureus</i>, <i>Streptococcus pyogenes</i>, <i>Streptococcus pneumoniae</i>, <i>Klebsiella pneumoniae</i>, <i>Pseudomonas aeruginosa</i> and <i>Haemophilus influenza</i>, and it was compared to that of grapefruit seed extract (GSE), a commercially available raw material commonly proposed as antibacterial ingredient for over-the-counter products. Procyanidins (PACs) and other polyphenols contents in LBE were determined by HPLC-FLD-MS and HPLC-DAD-MSⁿ, respectively. The antimicrobial activity of LBE and GSE was assessed using the micro-plate dilution technique in concentration range of 2-200 µg/mL, and the safety of these dosages was assessed in cellular and animal models. LBE showed considerable contents of PACs (15% <i>w</i>/<i>w</i>; especially B-type) and other polyphenols (3.8% <i>w</i>/<i>w</i>), among which the characteristic spiropolyphenols larixinol and epilarixinol were identified, together with the flavonoids isoquercitrin and rutin, already reported as growth inhibitors of different respiratory-tract pathogens. LBE showed higher antimicrobial activity compared to GSE, demonstrated by a growth inhibition range of 10-40% towards five of six strains tested, compared to 10-15% of GSE. These results suggest that LBE may represent a natural and sustainable source of active compounds with antibacterial activity for pharmaceutical and nutraceutical applications.

Item Description

10.3390/antibiotics10070789
2079-6382